1. Field of the Invention
The invention relates to the field of inspection and verification of semiconductor wafers or substrates during or at the end of production, or during the production of integrated circuits.
2. Description of the Relevant Art
As a result of the tendency to increase the diameters of semiconductor wafers, they must be handled with extreme care and are increasingly fragile. Furthermore, the increasingly fine engraving of the patterns of a semiconductor wafer makes each component of the wafer more and more susceptible to production faults.
In conventional manner, semiconductor wafers are visually inspected by an operator. The human eye is capable of detecting relatively small faults on semiconductor wafers which have, to the untrained eye, the appearance of a mirror. The greater the production quality, the better the human eye is capable of locating small faults. However, the fact that engraving techniques are becoming increasingly fine means that the human eye is reaching its limits, in particular for specific types of fault.
Furthermore, the task of visually inspecting semiconductor wafers is slow and fastidious. In a clean room for producing semiconductor wafers, it is desirable to reduce the presence of humans. Visual inspection is also found to be costly. The inspection machines are generally slow and bulky, which is a significant disadvantage in a clean room whilst using electromagnetic radiation which requires specific protection for the operators. Finally, the visual inspection does not generate adequate statistical data relating to the positions, sizes or types of fault, which is indispensable for the statistical monitoring of methods and research into the causes of faults or problems.